As mentioned in the last episode, ancient Chinese astronomers used the Armillary Sphere to measure the position of celestial bodies.

To use the Armillary Sphere, we need to understand the concept of the 28 mansions in ancient Chinese astronomy. The 28 mansions were used as reference points by ancient Chinese to describe the position of celestial bodies. Their names were carved on a certain ring of the Armillary Sphere.

In the Armillary Sphere there are three sets of rings: The outermost set is called the Ring of the Six Cardinal Points (Liuheyi), the middle one is the Ring of the Three Stellar Objects (Sanchenyi) and the innermost the Ring of the Four Movements (Siyouyi). This set comprises the Hour-angle Circle, Celestial Axis and a Sighting Tube. Embodying different astronomical concepts like the 28 mansions, the celestial equator, the ecliptic and the 24 solar terms, some of these rings are fixed while some are movable and can be turned manually.

Doing your head in? Don't worry! Let's just leave the complex structure of the Armillary Sphere aside. Next time when you visit the Astropark, do not forget to take a selfie with the Armillary Sphere. It is an exquisite piece of artwork that blends astronomy with art. Take a look at its features and learn about the astronomy behind it. It is also an excellent opportunity for us to appreciate the wisdom of our ancestors.

Let's think
1. How many circles are there in the Armillary Sphere?
2. The circles that can be turned in the Armillary Sphere share the same rotating axis. At which direction does this axis point?